Power watercraft (boats) moving at speeds when impacting a wave, either natural or caused by another's boat wake, technically experience three forces about mutually octagonal axis. These forces are commonly referred to as “roll” which is a force about an axis which is in line with the direction that the boat is headed, “pitch” which is about an axis which is a line in the same plane as the roll axis but ninety degrees orthogonal to the roll axis, and “yaw” which is an axis along a line which is vertical to, or ninety degrees from, both the pitch and roll axis.
In a traditional vessel, boat, cabin cruiser, etc., application, the operator of the watercraft is jarred substantially, even during mild seas. Standing while operating the vessel in such situations is practically impossible and the operator must be seated to avoid being thrown around uncontrollably.
Additionally, personal watercraft (PWC), defined herein as any low profile watercraft, have become popular. A PWC is a watercraft that is sporting in nature, turns swiftly, maneuvers easily and accelerates quickly. Typically, it carries one or two riders. Riders often experience noticeable vibrations, shocks and bumps as the relatively light-weight, small hull travels quickly across a body of water. These jarring movements are acerbated as the watercraft meets waves and wakes on the water. The resultant rough ride contributes to rider fatigue. Also, many riders jump their watercraft off of wakes and waves. The landing, however, severely jars the rider, especially if the watercraft lands bow first. The rider conventionally must absorb all of the impact by using his or her legs and arms.
A) Watercraft Suspension.
The prior art has recognized the need to address the safety, comfort and fatigue requirements of watercraft occupants. A number of seat suspension systems have been designed to address the needs discussed above.
In conventional watercraft, a number of suspensions for captain's seats have been developed. Reference can be had to U.S. Pat. No. 6,386,635 to Ralph, issued May 14, 2002, entitled “Shock Absorbing Boat Seat Assembly”; U.S. Pat. No. 5,044,299 to Frank, issued Sep. 3, 1991, entitled “Seat Construction for a Boat”; U.S. Pat. No. 5,639,059 to Nash, issued Jun. 17, 1997, entitled “Support for a Seat”; and, U.S. Pat. No. 5,911,191 to Burer, issued Jun. 15, 1999, entitled “Shock Absorbing Seat Pedestal,” all of which illustrate modifications to the pedestal on which the captain's seat rests to allow vertical pedestal movement. Typically, a seat pedestal, as a stand alone item, is mounted to the boat's deck and a captain's seat, as a stand alone item, is mounted to the pedestal. Mechanisms in the pedestal allow for height adjustment and mechanisms in the seat and/or pedestal allow for seat swivelling and swivel lock out. More particularly, in the mentioned patents, a spring biased, conventional shock absorber is mounted in a modified seat pedestal permitting a telescoping tubular movement for damping vertical forces imparted to the vessel's hull. Additionally, arrangements within the modified pedestal are made for damping lateral forces. For example, resistant material is disposed between the tubes in the '191 patent. For a lateral damping pedestal seat, see U.S. Pat. No. 6,179,255 to Radford, issued Jan. 30, 2001, entitled “Seat Mounting Assembly.” Additionally, see U.S. Pat. No. 6,042,093 to Garelick, issued Mar. 28, 2000, entitled “Boat Seat Shock Absorber,” for a description of a rubber isolator fitted into a pivoted clamshell for attachment between an existing pedestal and the captain's seat. All of the captain's seat arrangements discussed are passive. They are adjustable to the extent that hydraulic shock absorbers are known to be adjustable.
The suspension seat arrangements for PWC's generally use a hinged seat with the pivot adjacent one end of the seat and a shock absorber adjacent the other seat end. See for example, U.S. Pat. No. 5,603,281 to Harvey et al., issued Feb. 18, 1997, entitled “Watercraft Seat Suspension”; U.S. Pat. No. 6,182,590 to Patera, issued Feb. 6, 2001, entitled “Personal Watercraft Suspension System”; U.S. Pat. No. 6,152,062 to Hattori, issued Nov. 28, 2000, entitled “Small Watercraft with Improved Suspension System”; and, U.S. Pat. No. 5,367,978 to Mardikian, issued Nov. 29, 1994, entitled “Shock-Absorber Mounted Seat for Personal Watercraft and Boats.” In the '062 patent, the seat and a support frame carrying the seat are mounted to a three point, telescoping tube arrangement. In the '590 patent, an inflatable tube is mounted between seat and hull with the inflation pressure set at a desired level. All of the arrangements discussed are passive with the possible exception of one embodiment illustrated in the '978 patent. The '978 patent illustrates a possible solution to the sprung mass problem affecting PWCs where the weight changes from one to two passengers, but the shock absorber is tuned for one passenger. The '978 patent uses an air bag or air filled shock absorber powered by an electric pump to allow the air pressure of the shock to change for the sprung mass of the people carried by the PWC. Once changed, the system is passive as in the '590 patent.
In summary, the seats and/or seat suspensions employed in watercraft do use dampers, but the dampers are passive and do not have the ability to automatically adjust to the widely variant loads imposed on the seat in watercraft applications. That is, the hydraulic and pneumatic shock absorbers have fixed orifices through which fluid flows. The restriction in fluid flow caused by the orifice produces a damping force which is fixed for any set force applied to the shock, i.e., passive. If the shock is “tunable,” the shock orifice/flow arrangement is adjustable (within certain limits). However, once the shock's new flow arrangement is set, the damping force is also fixed. The typical passive shock absorber does not have the ability to sense a movement (resulting from an applied force) and change the valving of the shock, i.e., an active shock. Additionally, there are space limitations present in many watercraft installations which, in turn, affect the ability of conventional shock absorbers to provide an effective damper over the travel range of the dampers. Further, while air suspensions have been suggested to account for the different sprung masses to which the PWC seat may be exposed, an external source of fluid, i.e., air pump, has to be provided and the damper curve for air shocks is limited.
B) M-R Dampers.
Generally, dampers utilize fluids for controlling the relative movement of the mechanical parts. For example, hydraulic fluid may be utilized as a medium for creating damping forces, or torques, or controlling motion, shock and vibrations. One class of such movement control devices utilizes a fluid medium which has characteristics which are controllable through the use of magnetic fields and/or magnetic flux and the present invention relates to this class of control devices. Such magnetically controlled fluid is referred to as magneto-rheological, or M-R, fluid and is comprised of small, soft magnetic particles dispersed within a liquid carrier. The particles are often generally round, and the suitable liquid carrier fluids include hydraulic oils and the like for suspending the particles. M-R fluids exhibit a thickening behavior (a rheology change), often referred to as “apparent viscosity change,” upon being exposed to magnetic fields of sufficient strength. The higher the magnetic field strength to which the M-R fluid is exposed, the higher the flow restriction or damping force that can be achieved in the M-R device, and vice-versa. That is, the flow properties of M-R fluids may be selectively altered by magnetic fields.
A typical M-R damping device, for example, utilizes an iron core structure disposed within or surrounded by a metal cylinder or casing. M-R fluid is positioned to flow between the core and the metal cylinder. The damping effect of the device is due to the relative movement of the core and cylinder with respect to the M-R fluid or vice-versa. That is, depending upon the use and structure of the M-R damping device, the core and cylinder are dynamic and move through the M-R fluid or the M-R fluid moves between a stationary core and cylinder. To control the damping effects of the device, a magnetic flux is formed in and around the core and the metal cylinder, such that the core and cylinder create a magnetic circuit. The metal cylinder or casing surrounding the core is often referred to as a “flux ring” as it directs and provides a path for the magnetic flux which exists in and around the core. Variation of the flux in the device affects the flow of the M-R fluid between and around the core and flux ring and thus allows variation of the damping effects of the M-R device.
More specifically, during operation of the damping device, the M-R fluid flows through a restricted passage or gap formed between the flux ring and the core. Magnetic flux exists within the gap, and therefore, the characteristics of the M-R fluid flow through the gap are magnetically controlled by controlling the magnetic flux. By controlling the characteristics of the M-R fluid flow, the movement of the core and flux ring relative to the fluid is controlled, thus creating a damping effect to the physical structures which are operably coupled to the M-R damping device. To form and vary the magnetic flux in and around the core and within the gap between the core and the flux ring, a magnetic field generator, such as a wire coil, is wound around the core. The magnetic flux in the core and in the fluid passage is varied by variation of the electrical current through the coil. The selectively variable magnetic flux dictates the characteristics of the fluid flow in the restricted passage. The relative movement between any mechanical parts and the damping of that movement is then regulated by controlling the characteristics of the fluid flow.
When constructing and assembling a typical M-R damping device as described above, the core and the wire coil, which is wound around the core, are formed with an insulative material. The material, which may be an insulative plastic material, is molded flush around the coil to protect the coil form the M-R fluid. Thereafter, the flux ring, or other metal casing surrounding the core and coil, is placed around the core and coil.
It is to be appreciated that the magnetic field changes instantaneously and the apparent viscosity and the shear resistance of the M-R fluid will change accordingly, i.e., within fractions of a millisecond. Accordingly, as disclosed in assignee's United States patent publication No. 2002/0153647 A1 to Baudendistel et al., published Oct. 24, 2002, entitled “Hydraulic Mount and Control Method,” there is disclosed a control system sensing pressure of the M-R fluid in one of the shock absorber chambers. The sensed pressure is then utilized by a controller vis-a-vis an algorithm to vary the magnetic flux and “apparent viscosity” of the M-R fluid in the gap to produce a desired damping force. The damping force is directly determined by the instantaneous external force imposed on the damper causing the sensed pressure in the damper's chamber. The damper is thus active because the damping force is determined by the external force applied to the damper.
C) Hydraulic Dampers.
Still further, the assignee of the subject invention has developed hydraulic dampers for motor mounts and automotive suspensions which are active dampers. As is well known in the hydraulic damper art, damper orifices are sized so that the damper is tuned to provide damping forces to null out vibration frequencies within set ranges. Motor mounts are exposed to widely different force frequencies. Automotive suspensions are frequently subjected to driving conditions requiring a firm or soft suspension. The assignee has developed hydraulic damping systems which sense applied forces and in response to the sensed force, adjusts the effective orifice size of the hydraulic damper so that the damper is tuned to damping frequencies typically falling within one of two ranges. The damper is active because it is tuned to a frequency range corresponding to the actual forces experienced by the motor mount. Reference can be had to U.S. Pat. No. 5,690,195 to Kruckemeyer et al., issued Nov. 25, 1997, entitled “Alternating State Pressure Regulation Valved Damper”, and U.S. Pat. No. 5,706,919 to Kruckemeyer et al., issued Jan. 13, 1998, entitled “Alternating State Pressure Regulation Valved Damper”, for examples of two-stage dampers.